This invention relates generally to skateboards and, more particularly, to skateboards incorporating truck assemblies configured to minimize hanger-jiggle and wheel bite.
Skateboards typically include an elongated platform having a pair of truck assemblies mounted at the opposite ends of its underside. Each truck assembly incorporates a base plate secured to the platform and an axle/wheel assembly having a pair of wheels for propelling the skateboard along a path generally aligned with the skateboard""s longitudinal axis. The axle/wheel assembly includes an axle that mounts the two wheels at its opposite ends, and it further includes a pivot stem that projects radially outward from a mid-portion of the axle for seating in a recess formed in the base plate. A ring-shaped hanger also projects radially outward from a mid-portion of the axle, at a prescribed acute angle (e.g., 45 degrees) relative to the pivot stem, for engagement with a kingpin that projects downwardly from the base plate. Upper and lower bushings secure the hanger around the kingpin.
The truck assemblies described briefly above are configured to enable a rider to steer the skateboard simply by shifting his/her weight distribution rightward or leftward on the skateboard platform. This weight shift causes the platform to tilt correspondingly relative to the axles of the two truck assemblies, which remain at all times level relative to the ground. The axles thereby are caused to pivot horizontally about the axes of their associated kingpins, which in turn causes the skateboard to steer rightward or leftward. Riders generally desire to steer the skateboard using very slight shifts in their weight distribution. Loose or slack bushings generally allow greater movement of the ring-shaped hanger about the kingpin and thus are more responsive to slight weight shifts than are tight suspensions. However, loose or slack bushings can fail to prevent certain undesired ride characteristics.
One such undesired ride characteristic is hanger-jiggle, which occurs when the axle and hanger are allowed to move laterally relative to the axis of the kingpin. This can cause instability in the platform. Another such undesired ride characteristic is wheel bite, which occurs when the axle pivots excessively relative to the kingpin, to an extent that a wheel contacts the underside of the skateboard platform. This brakes the wheel and disturbs the rider""s balance.
In the past, these undesirable ride characteristics typically have been avoided by tightening the bushings against the hanger. This tightening, however, can reduce the skateboard""s steering responsiveness. It should, therefore, be appreciated that there is a need for a skateboard truck assembly that eliminates undesired ride characteristics such as hanger-jiggle and wheel bite, without sacrificing the skateboard""s steering responsiveness.
Skateboard riders sometimes perform maneuvers called slides, in which a contact surface of the skateboard other than the wheels is made to slide along a fixed structure, such as a rail or a concrete wall. Because such riders typically seek to maximize the duration, speed and distance of the slides, a minimum loss of momentum is desired. However, friction between the skateboard""s contact surface and the fixed structure can cause an excessive loss of momentum. This can make the maneuver difficult to perform and can damage the truck assembly. It should, therefore, be appreciated that there is a need for skateboard truck assembly configured to minimize a loss of momentum when the skateboard is used in a slide maneuver.
The present invention is embodied in a skateboard truck assembly configured to eliminate undesired ride characteristics such as hanger-jiggle and wheel bite, without sacrificing the skateboard""s steering responsiveness. More particularly, the""truck assembly includes a base plate configured to be secured to the underside of a skateboard platform and further configured to have an underside that defines a pivot recess. A kingpin projects downwardly from the underside of the base plate, at a predetermined angle toward the pivot recess, along the skateboard""s longitudinal axis. The truck assembly further incorporates an axle/wheel assembly that includes 1) an axle, 2) first and second wheels mounted for rotation at opposite ends of the axle, 3) a ring-shaped hanger that projects from a mid-portion of the axle and defining an opening sized to be larger than the kingpin""s cross-section, and 4) a pivot stem that projects from a mid-portion of the axle for seating in the pivot recess. The axle/wheel assembly is mounted on the underside of the base plate with the axle oriented substantially perpendicular to the skateboard""s longitudinal axis, with the pivot stem seated in the pivot recess, and with the hanger disposed around the kingpin, such that an annular gap is defined between the hanger and the kingpin. Finally, a bushing assembly is disposed on the kingpin, adjacent to the ring-shaped hanger, wherein the bushing assembly is sized and configured to inhibit both axial and lateral movement of the hanger relative to the kingpin, while permitting limited pivoting of the hanger about the axis of the kingpin.
In more detailed features of the invention, the bushing assembly includes first and second bushings that encircle the kingpin on opposite sides of the hanger, such that the hanger is sandwiched between them. At least one of the bushings includes an annular flange sized to fit into the annular gap defined between the hanger and the kingpin. The annular flange can be defined in just one of the bushings and an annular recess can be defined in the other bushing, for conformably receiving the annular flange. The bushings cane molded of polyurethane.
In another feature of the invention, the base plate is configured to include a generally flat upper surface for securement to the underside of the skateboard platform, and one or more protrusions can project upwardly from this surface for engagement with the platform. This enhances the securement of the truck assembly to the platform.
In a separate, independent feature of the invention, a low-friction slider plate can be secured to the base plate, on the side of the truck assembly opposite the kingpin. This minimizes friction between the skateboard and any fixed support structure during certain maneuvers. The slider plate can be flush with, or extend slightly beyond, the base plate. The slider plate can be located in a position such that it retains a pivot cup that defines the recess for seating the truck assembly""s pivot stem.
Other features and advantages of the present invention will become apparent from the following description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.